What is Avian Botulism?
Botulism is a neuromuscular disease caused by the bacterium Clostridium botulinum. There are several different types of botulism. Type C and type E are responsible for extensive waterfowl die-offs and some fish kills. Type E is more prevalent in the Great Lakes. Botulism in humans is usually caused by type A or B and results from consuming improperly home-canned foods.
In the Great Lakes, botulism spores (the resting stage of the bacteria) are abundant in anaerobic habitats, such as soils, and aquatic sediments of many lakes. When the correct environmental factors are present, the spores germinate and begin vegetative growth of the toxin-producing bacterial cells.
An estimated 7,500 waterbirds in November 2007 and 2,900 waterbirds in 2006 died on Lake Michigan, poisoned by eating fish that carried the toxin. One theory is that infected fish, partially paralyzed by the toxin, became easy prey for flocks of migrating waterbirds. See: Upwellings March 2007 (PDF)
Scientists believe that outbreaks of type E botulism occur only when particular ecological factors happen simultaneously, such as warmer water temperatures, anoxic (oxygen deprived) conditions, and nutrient-rich substrate, or areas with large amounts of decaying plant growth. As average air and water temperatures have been rising on a global scale, warmer temperatures and anoxic conditions are occurring more frequently. Once these factors lead to the production of the toxin in food material eaten by fish, the toxin can be passed up the food chain as birds consume the infected fish.
Botulism has been identified as a problem for fish and birds in Lakes Ontario and Erie, and in Lake Michigan. For more information about avian botulism:
General Information About Botulism
- Frequently Asked Questions
- Type E Botulism Outbreaks: A Manual for Beach Managers and the Public (PDF)
- Botulism Fact Sheet (PDF)
- Ecology of Type E Botulism Within Dreissenid Mussel Beds (PDF)
- 2005 Botulism Workshop
Botulism in Michigan
- DNR Confirms Birds Positive with Type E Botulism in Mason County (Michigan DNR News Release, August, 2008)
- U.S. Environmental Protection Agency
- Michigan DNR botulism website
- State of Michigan website on Emerging Disease Issues
- Sleeping Bear National Lakeshore
Contact: Mark Breederland